Why the First Eight Weeks Are a Biological Window
A puppy is born with borrowed immunity. Maternal antibodies passed through colostrum, the first milk, give a newborn temporary protection against diseases the mother has been vaccinated against or exposed to. According to research published in the journal Veterinary Immunology and Immunopathology, this maternal immunity begins to wane between six and eight weeks of age, creating a window where the puppy is increasingly vulnerable and where active vaccination must begin. The problem is that residual maternal antibodies can also partially neutralise a vaccine if it is given too early, which is why the schedule is timed the way it is, not arbitrarily, but around this immunological handover.
